The invention is directed to a carbon black concentrate, its production and its use as a pigmenting material in lacquers or printing inks.
Carbon black is added to a great extent in the production of black lacquers and printing inks. There exists in carbon blacks in a known manner a dependency between the blackness and the primary particle size. Deep black carbon blacks corresponding to a higher surface area have a lower primary particle size. Carbon blacks with a lower degree of blackness on the contrary have larger primary particle sizes and relatively low surface areas. Carbon blacks with high surface areas generally are poorly dispersible in liquid binding agent systems. Therefore, a high amount of dispersing work must be expanded to distribute these carbon blacks in binders for lacquers and printing inks and to open up the optimum capacities of these carbon black qualities in the dispersing.
Known apparatus which are used to distribute pigments in thinly liquid binder systems are for example ball mills or bead mills. Known apparatus which are used to distribute pigments in viscous plastic binder systems are for example intermittent or continuous kneaders. These apparatus, however, mean a high energy expense. Furthermore, there are a number of binders which cannot tolerate the high temperatures that for example are developed in the kneading and can be decomposed either slowly or explosively.
In order to eliminate these difficulties there have been endeavors to produce carbon black concentrates in the particular binders. These carbon black concentrates then need merely be swollen in solvents and be introduced into the particular lacquer or printing inks without special shearing forces in order to produce the desired lacquer or printing inks. In order to attain a good dispersion of finely divided carbon blacks of larger surface area without a too high loading of the binder there have been endeavors to improve the dispersibility of the finely divided carbon blacks by addition of dispersing agents. Particularly important is the use of a dispersing agent in the working up of nitrocellulose binders because in this case a too strong mechanical working in of the carbon black can lead to explosive decomposition of the nitrocellulose. The quality of the carbon black-binder preparation is frequently decisive for the type of dispersing agents. In selection of the dispersing agent is is important that this dispersing agent produce no negative properties or changes in the final systems in which it is added.
In known carbon black concentrates there are primarily used as dispersing agents amine containing compounds, as, e.g., benzidine and phenylene diamine. The amines usable as dispersing agents have poor solubility in test gasoline or xylene. This forms pimples and spots in the lacquer coating insofar as there is not carried out an additional operation for clarification, as, e.g., centrifuging. Their use as pigmenting agents because of their amine content is physiologically objectionable.